Carburetor



Patented July 13, 1948 CARBURETOR Emil 0. Wirth, South Bend, Ind., assignor to Bendix Aviation Corporation, South Bend, Ind., a corporation of Delaware Application December 27, 194s, serial No. 515,727

s claims. (ci. zei-ss) This invention relates to fuel feeding systems for internal combustion engines and more particularly to mixture control and fuel cut-olf devices for systems of this character which are generally used on aircraft and in which liquid fuel is supplied to the engine under superatmospheric pressure and is metered while being maintained under pressure.

Some fuel systems of the foregoing character include a manual mixture control device for varying the richness of the mixture and means for cutting ofi the flow of fuel to the engine. In such systems it is known vto arrange the manual mixture control device and fuel cut-ofi valves so that actuation of the mixture control valve may effect actuation of the fuel cut-off valve. is not always desirable to actuate both valves solely by the same actuating means for under some circumstances it may be desirable to cut off the fuel flow to the engine without altering the position of the valve of the mixture control device and it is therefore an important object of fecting the position of the valve of the mixture control device, as well as providing means whereby both valves may be actuated together.

Another object of the invention is to provide a device of this character wherein the mixture control valve may be adjusted independently of the cut-off valve.

Still another object of the invention is to provide a device of this character wherein the means for actuating the cut-off valve, independently of the mixture control valve, is eiected by electrically operated means.

It is a further object of the invention to provide a device of this character wherein electrical means for independently controlling'the cut-off valve is operated in connection with the ignition switch of the engine. This is desirable as it reduces the number of switches and the like which the operator must actuate in starting and stopping the engine and the arrangement has a further advantage in that both the fuel supply and ignition are cut off simultaneously.

A still further object of the invention is to provide a device of this character wherein novel improvements reside in certain details of construction, arrangement, and combinations of the parts. i

Another object of the invention is to provide a simplified device of this character which may be built at reasonable cost and which is accurate and reliable in operation.

However, it

Other objects and advantages of the inventio will be readily apparent to those skilled in the art from the following description taken in connection with the accompanying drawings, which represent a preferred embodiment. After considering this embodiment skilled persons will understand that many variations may be made without departing from the principles disclosed; and I contemplate the employment of any structures, arrangements, or modes of operation that arevproperly within the scope of the appended claims.

In the drawings:

Figure 1 is a diagrammatic sectional view of a fuel feeding system embodying the present invention; and

Figure 2 is a partial section of same showing a modification of the invention.

With reference to Figure 1, there is `shown a main body member Ill which contains an induction passage l2 therethrough having an air inlet I4 and an outlet I6, the air inlet being provided with an outer surface I8 to which an air scoop (not shown) opening in the direction of travel may be secured and the outlet I6 being provided with flanges (not shown) for securing the body member I0 to the manifold of an internal combustion engine or to the inlet of a supercharger if one is used between the carburetor and the manifold. If desired, a supercharger may be used anterior to the body member I0 either in place of or in addition to a supercharger posterior to said body member. A venturi 20 having separable inlet and outlet sections is positioned in the induction passage adjacent the inlet I4 and is formed with an annular chamber 22 which communicates with the interior of the venturi through an annular slot 24 to be thereby subjected to Venturi depression. An annular `chamber 26 is in free communication with the air entering the venturi through an annular opening 28, the opening 28 being preferably subjected to the impact pressure of the air supplied to the venturi. A throttle 30 is pivotally mounted in the induction passage posterior to the venturi and is adapted to be manually actuated to control the air flow to the engine.

The fuel flowv to the engine is regulated or controlled by an unmetered fuel pressure control unit or regulator, indicated generally at 32, which regulates or determines the fuel pressure on the upstream side of a fuel metering jet system diagrammatically illustrated as jet or orice 34 and by a discharge nozzle assembly indicated generally at 36 which regulates or determines the pressure on the downstream side of the metering orifice 84. It will be understood that the metering jet system 84 might consist of some other arrangement than that above described such as any well known conventional system of jets wherein the effective fuel metering area is varied to provide power enrichment, idling or running mixture richness control, or altitude richness control.

The interior of the regulator unit 82 is divided into three chambers 48, 42 and 44 by diaphragms 48 and 48. As shown the diaphragms A46 and 48 have an area ratio of one-half although, as will be apparent hereinafter, any desired area ratio may be used. 'I'he center portions of the diaphragms are supported by thin plates 58 between which the diaphragms are clamped by centrally disposed rivets 52 and 54 under the deformed ends of which washers 58 may be provided so that the thin plates will not tear loose from the rivetedover portion of the rivets. I'he rivet 52 is provided -with a cylindrical recess and rivet 54 is provided with a shank 55, one end of which is freely received in the recess of the rivet 52, said end of shank 55 being preferably rounded to form an angularly adjustable one-way connection with the diaphragm 88 whereby slight misalignment of said diaphragms may be accommodated without binding. This construction also greatly facilitates assembly and disassembly of the control unit 82.

Chamber 48 is provided with a fuel inlet port -controlled by a valve 88 and receives fuel fromY a source of fuel under pressure, such as a fuel pump (not shown), through a pipe 82. The valve 88 has a pin-like extension projecting into the chamber 48 in position to be engaged by the head of rivet 52 whereby movement of the diaphragms to the right, as shown by the drawing, opens the valve. A spring 84 urges the valve toward its closed position. lA spring 88 isY mounted at one end in the chamber 44 and has its free end received in a spring retainer portion of a lever 88 pivotally mounted at one end and having a crimped center portion normally engaging the head of rivet 54 and urging the diaphragms to the right in a direction to open the valve 58. The spring 88 may be rendered inoperative, when the engine is to be stopped, by a plunger 18 which therefore subjected to a pressure primarily defrom the fuel inlet 82 passes through the fuelmetering jet system diagrammatically illustrated by the metering orifice 84, thus becoming metered fuel which is transmitted through a pipe 88 to a chamber |84 of the discharge nozzle assembly 88. The chamber |84 of the nozzle assembly 88 is separated from a chamber |58 by a preformed annularly grooved diaphragm |52 connected to a fuel outlet valve |54 which is urged to the rig-ht, in a direction to close the valve, by a spring |58 arranged to be variably loaded by an adjustment screw |58, said chamber |58 being connected to the Venturi annulus 22 by the passage 18. The stem of valve |54 is of triangular cross section or otherwise relieved to permit fuel flow therepast to a fuel discharge nozzle indicated generally at |58 and is slidable within a nozzle bar |88 of the nozzle |58. In this arrangement the valve |54 is not fixed to the diaphragm |52 but is maintained in abutting relation therewith by means of a light spring |82 which constantly urges t'he valve |54 to the left. This arrangement eliminates any tendency for the valve to bind in its valve guide and seat member |84 as a result of misalignment between the diaphragm and the guide member.

The calibrated passage 88 interconnects the chambers 42 and 44 and is controlled by the mixture control valve 82 which is urged in the closed direction by a spring |88. Valve 82 may upon downward movement thereof engages theI x free end of lever 88 and moves the lever to the left against the force of spring 88. The lever 88 will thus move out of engagement with the rivet 54 whereby the fuel pressure in chamber 48 will move the diaphragm 48 to the left and permit the spring 84 to close the valve 88 and cut off the fuel supply tc the engine. In order to eliminate vapor, 4a pipe 12 having a restricted communication 18 with the top of chamber 48 may be provided, said pipe leading Iback to the fuel supply tank.

The chamber 42 of the regulator unit 32 isA connected to the Venturi annulus 22 by means of pipes 15, 82 and a passage 18 in the body I8, and is therefore subjected to a pressure primarily derived from the throat of the venturi 28. A restriction 18 may be provided in passage 18 if desired. The chamber 4'2 is also connected to the air scoop or Venturi entrance by means of a calibrated passage 88, controlled -by a manual mixture control valve 82, a passage 84, the annular chamber 28 and annular opening 28. The chamber 44 of the regulator unit 82 is connected to the annular Venturi entrance chamber 28 by a branch passage 85 of the passage 84 and is be independently adjusted as desired from the pilots compartment by a cable actuated member |88. A cable (not shown) is connected to the member |68 and said cable leads to the pilots compartment where it is attached to a cable actuating device (not shown) of any well known character whereby actuation of the cable will effect corresponding movement of the valve 82. This adjustment is manually effected and provides the pilot with means for manually regulating the richness of the fuel mixture to meet the requirements of the engine under various operating conditions. The stem of said valve 82 is provided with a conical collar |18 which is adapted to engage a pivoted lever |12 to force the plunger 18 downwardly when the mixture control valve is moved beyond its wide open or lean position to its idle cut-off position for effecting closing of valve 88 to cut of! the fuel flow to the engine. lMeans for eilecting closing of the fuel valve 88, independently of the valve 82, comprises a solenoid |88 which has an axial bore within which a plunger |84 is slidable. Thev plunger |84' has an extension |88 connected with lever |12 adjacent the upper end thereof. there being a stop |88 for limiting movement ofthe plunger |84 to the left as viewed in the drawing. The

'air differential pressure.s

decrease in the pressure in the Venturi chamber ably being located conveniently ln the pilot's compartment of the aircraft.

Operation urge the diaphragms to the right and open the valve 88 Fuel under pressure supplied to pipe 82 enters and fills chamber 48 and flows through the Jet I4 and pipe 88 to the chamber |84. vAsthe pressure in chamber 40 increases it acts against the diaphragm 48 and tends to compress spring 88 whereby the valve 6,8 tends to close. Fuel under pressure supplied to chamber |84 acts on diaphragm |52 and tends to open valve |54. The screw |88 is normally adjusted to compress spring |88 to such a point that a slightly lower pressure is required in chamber |04 to open the valve |84 than is required in chamber 40 for sufficiently compressing the spring 68 to permit the valve 88 to close. Once the carburetor'has been fully filled with fuel, fuel will therefore slowly spill .from the discharge groove |6| ofthe fuel nozzle,

made greater than, equal to or less than the` pressure required in chamber 48 to permit the valve 88 to close. It will also be apparent that the actual value or degree of the fuel pressures lwill be determined by the strength of the springs 88 and |58, t'he pressure required being greater as the Istrength of the springs is increased.

Durlng'oper'ation, assuming the area ratio of the diaphragms 48 and 46 is equal to two, the regulator unit ufunctions to maintain a differential fuelpressure across the metering unit I4 which is equal to twice the venturi to entrance For example, a given 22 is transmitted to' the chamber 42, where it results in an equal increment increase in the unmetered fuel .pressure in chamber 46, and is transmitted to chamber |84, where it results in an equal increment decrease in the metered fuel pressure. Consequently the fuel metering differential pressure is increased in amount double the increase in the air differential. Similarly a given increase in the entering air pressure in the chamber 26 is transmitted to chamber 44 and since it is applied to the diaphragm 48 having twice the area of diaphragm 48. the unmetered fuel pressure in chamber 881s increased an increment double the increase in `entering air pressure.

Although the diaphragms 48 and 46 are shown as having a two-to-one area relationship, they may be of any other desired area ratio, in which case the fuel metering differential ,pressure will` be maintained at some multiple, other than two, of the air differential pressure. For example, if the area of diaphragm 48 is three times the area of diaphragm 48, the fuel differential will be maintained equal to three times the air metering differential. Or, if diaphragms 48 and 48 are of equal size. the fuel metering differential pressure is maintained substantially equal to the air dierential pressure. In any event, the fuel and air differential pressures are maintained in constant proportion and therefore constant fuel to air proportioning is obtained.

The automatic mixture control .unit 86, or altitude control unit, as it is sometimes referred to, is provided to maintain a constant mixture richness with variations in altitude. Upon a decrease in the density of the air entering the venturi, as by increase in altitude, the differential between the entering air and the Venturi pressures will increase for a constant weight of air flow ,per unit of time and will tend to increase the fuel flow and enrich the mixture. As the' density increases, however, the bellows 91 expands, be-

cause of a, decreased pressure on the exterior of the bellows, and moves valve 84 downwardly to increase the area of communication between the pipes 88 and 82. Airis thus bled into the chamber 42 to thereby reduce the differential .pressure which would otherwise exist between the chambers 42 and 44, whereby unmetered fuel pressure in chamber 48 is increasingly decreased. By properly contouring the valve 84, the differential in the air pressures in chambers 42 and 44 are so controlled that the fuel supplied to the engine remains constant for a given weight of air flow per unit of time even though the entering air density changes.A Automatic altitude compensation is thus obtained.

It is generally considered desirable in carburetors of this character to provide the pilot with a manual mixture control so that he can manually regulate or vary the richness of the mixture between predetermined limits to 1provide the proper fuel mixture required by the engine under various operating conditions. Such regulation of the mixture is effected by the valve 82 which controls the calibrated passage 88 and said valve 82 is adjustable from a position whereat the passage 8|| is completely closed to a position whereat passage 88 is fully open. A rich setting is effected by closing the valve 82 and as saidkvalve is opened air is bled from the air scoop chamber 44 into the Venturi chamber 42 whereby the differential pressure between these chambersis reduced an amount depending upon the extent the valve 82 is opened. This in turn reduces the unmetered fuel .pressure in chamber 40 to maintain the diaphragm assembly in an equilibrium position, thus reducing the fuel metering differential and consequently reducing the richness of the mixture for a given air flow. With the valve 82 completely withdrawn the carburetor is in its full lean position, the eiective area of passage 88, as limited by the seat of valve 82, determining the maximum permissible bleeding action. The manual mixture control valve 82 and the automatic mixture control unit 96 control the pressures in the `chambers 42 and 44 and also have some effect on the pressure in the chamber |50 of the valve assembly unit 36.

When the engine is to be stopped it is desirable to cut oi all fuel flow thereto so that it will not continue to run, as a result of pre-ignition, after the ignition is turned off. To accomplish this end. the valve 82 is moved upwardly beyond its full lean position to an idle cut-off position at which the plunger 18 is forced downwardly, by the ac-` tion of 'collar |10 on lever |12, whereby lever 68 is forced to the left and the spring 88 is compressed and the light spring 84 is able to fully close valve 60.

As pointed out above it may be desirable, under certain conditions. to cut off the fuel flow to the engine without altering the .position of the valve I2. as when said valve I2 is adjusted for some particular operating condition and it is desired to retain this adjustment so that the fuel mixture will be the same when the engine is restarted as when it was stopped. Under such conditions the fuel may be cut oil' by closing switch |22 of the solenoid circuit thereby effecting actu ation of the lever i12 to force plunger 1l downwardly thereby compressing spring II and effecting closing of valve 6l as above described.

If desired the solenoid controlling the fuel cutoi valve may be controlled simultaneously with the ignition switch as shown in Figure 2 wherein the solenoid I" is controlled by ignition switch 2 II so that when said switch is closed the solenoid is energized and when the switch is opened the solenoid is deenergized. The solenoid plunger 2 I2 is connected with the lever |12 by a rod 2 I 4. A relatively heavy spring 2H. disposed about the rod 2M, reacts between a fixed member 2l! and a member 220 secured to said rod, said spring being adapted to urge the rod to the left in a direction which will effect movement of the upper end of the lever 88 to the left and permit closing of the cut-off valve 60 by spring 84. It is to be noted that the spring 2 I 6 is of sufficient strength to overcome the force of spring 8l.

Normally when the solenoid I III is deenergized spring 2|'6 urges rod 2M to the left until member 220 abuts against portion 222 of the solenoid assembly at which time lever i8 is moved to a position which will permit valve il to close. vUpon closing of the ignition switch 2N the solenoid is energized and moves plunger 2I2 to the right against the force of spring 2 I 6 until the lower end of lever |12 engages stop 224. Spring t6 then is freed to eiect opening of valve l0.

Should it be desired to eil'ect closing of valve il when the solenoid is energized the mixture control valve 82 is moved upwardly until the conical collar |10 engages the upper end of lever I12 and actuates said lever in the manner hereinabove described in connection with Figure l, it being understood of course that valve l2 may be moved from its fully closed to its fully open position without effecting actuation of lever I'l2. Thus it will be apparent that in both embodiments of the invention the mixture control valve 82 may be moved throughout its effective range as a valve without effecting the position of the cut-olf valve 6B. Further both the manual mixture control valve 82 and the valve 60 may be controlled simultaneously, and the cut-olf valve 60 may be independently controlled without effecting the position of the mixture control valve 82.

From the foregoing it will be understood that many changes may be made in the form and arrangement of the parts of the present invention without departing from the spirit and scope thereof or sacrificing all of its material advantages and itis not intended that the scope of the invention shall be limited to the form shown and described nor otherwise than by the terms of the appended claims.

I claim:

1. In a fuel supply system for internal combustion engines: an air supply passage; a fuel supply conduit; a cut-off valve controlling said conduit; means including a mixture control valve for controlling the richness of the fuel mixture delivered to the engine; means so constructed and arranged to control both of said valves; and electrically operated means adapted to control the first mentioned valve independently of the means for controlling both valves.

2. In a fuel supply system for internal combustion engines wherein the fuel is supplied to the engine under super-atmospheric pressure and is metered while being maintained under pressure; a fuel conduit having metering means' therein; a fuel cut-olf valve which when ,closed prevents fuel from flowing through said conduit to the engine; a mixture control valve for controlling the richness of the fuel mixture delivered to the engine; means so constructed and arranged asy to control both said valves; and means adapted to control the first mentioned valve'independently of the means for actuating both of said valves. 3. The inventiondened by claim 2 wherein the means for controlling both of said valves is manually operated and the means for controlling the cut-olfvalve is electrically operatedf l.

, 4. The invention defined by claim 2 wherein the means for controlling the cut-off valve independently of the means for controlling both of said valves includes an electrically operated solenold.

5. In a fuel feeding system for internal combustion engines in which liquid fuel is supplied t0 the engine under superatmospherlc pressure and is metered while being maintained under pre..- sure: means for regulating the unmetered fuel pressure; means for regulating the metered fuel pressure independently of the means for regulating the unmetered fuel pressure; a fuel cutoi valve; means including a valve for modifyind the richness of the fuel mixture delivered to the engine; means for simultaneously controlling both of said valves; and electrically operated means for controlling the cut-oli' valve independently of the second mentioned valve.

6. In a charge forming device: an air passage; a venturi therein; a throttle valve in the passage posterior to the venturi; a fuel conduit; a metering restriction in the conduit; means including a valve in the conduit anterior to the restriction and a pair of diaphragms urged in the opposite directions by the pressure in the air passage, the air supply pressure and by unmetered fuel pressure for controlling only theunmetered fuel pressure; means including a valve in the conduit posterior to the restriction and a diaphragm urged .in opposite directions by the pressure at the venturi and by metered fuel pressure for controlling only the -metered fuel pressure; means including a mixture control valve for controlling the richness of the fuel mixture delivered to the engine; manual means for controlling the first mentioned valve and the mixture control valve; electrically actuated means for controlling the first mentioned valve independently of the mixture control valve; and a valve operated automatically in response to variations in pressure resulting from variations in altitude for controlling the richness of the mixture delivered to the engine.

7. In a fuel supply system for internal com- Y bustion engines wherein the fuel is supplied to fuel cut-o valve independently of the first mentioned means.

8. In a fuel supply system for an internal combustion engine wherein the fuel is supplied to the engine under super-atmospheric pressure and is metered while being maintained under pressure; a fuel conduit having metering means therein, a. mixture control valve for controlling the richness of the fuel mixture delivered to the engine; a fuel cut-off .valve in said conduit; a member on the mixture control valve; means adapted to be actuated by said member only when the mixture control valve has been substantially fully opened for eiecting closing o f the fuel cut--y off valve; and means adapted to close the fuel cut-off valve independently of the first mentioned means when the mixture control .valve is in a less open position than that whereat the member thereon will effect closing of the cut-oil valve. l

EMIL O. WIRTH.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED sTATEs PATENTSl Certificate of Correction Patent No. 2,445,097. July 1,31948.

EMIL o. WIRTH` Itis hereby certified that errors appear in-the'iirinted specification of t i numbered petent requiring correction as follows: f y

Coinmn 8, line 74, claim 7, after the Word Ineens strike out the Word isfv` and insert instead Teaches a posztion; line 75, after movement and before the semicolon, insert 'whereat send first mentioned valve is fully open;

and that the said Letters Patent should be reed with these corrections therein thet the seme may conform to the record of the oase in the Patent Oee.

.Signed and sealed this 14th dey of December, A. D. 1948.

THOMAS F. MURPHY,

Assistant Uommz'ssz'oner of Patents. 

